Salesforce's Benioff in Seattle last year.

Microsoft filed suit this afternoon against Salesforce.com, alleging that the San Francisco company's customer-relationship management technology violates nine of its patents. The complaint, in U.S. District Court in Seattle, seeks an injunction against Salesforce and unspecified monetary damages.

The case is sure to spark a response from Salesforce and its chief executive. Marc Benioff, who has been an outspoken critic of the Redmond company. Although Microsoft has been a frequent target of patent-infringement claims itself, it's only the fourth time in its history that the Redmond company has filed a patent-infringement suit against a competitor, and the company has said in the past that it views such actions as a last resort when it has been unable to negotiate a licensing deal.

Here's the full text of the complaint: PDF, 10 pages.

[Follow-up: Microsoft vs. Salesforce: Dispute includes basic software updates]

"Microsoft has been a leader and innovator in the software industry for decades and continues to invest billions of dollars each year in bringing great software products and services to market," said Horacio Gutierrez, corporate vice president and deputy general counsel of Intellectual Property and Licensing, in a statement. "We have a responsibility to our customers, partners, and shareholders to safeguard that investment, and therefore cannot stand idly by when others infringe our IP rights.”

We're reaching out to Salesforce for comment now. Stay tuned for updates.

Update, 3:30 p.m.: A representative of Salesforce.com said the company isn't yet commenting on the litigation.

As noted by Ina Fried of CNet News.com, the Salesforce has made reference in regulatory filings to receiving "a communication from a large technology company alleging that we were infringing upon some of their patents."

"We continue to analyze the potential merits of their claims, the potential defenses to such claims and potential counter claims, and the possibility of a license agreement as an alternative to litigation," Salesforce continued in a January filing. "We are currently in discussions with this company and no litigation has been filed to date. However, there can be no assurance that this claim will not lead to litigation in the future. The resolution of this claim is not expected to have a material adverse effect on our financial condition, but it could be material to the net income or cash flows of a particular quarter."

Microsoft most recently filed suit and subsequently reached a settlement in a patent dispute with navigation company TomTom.

That case was notable in part because it involved allegations over TomTom's implementation of Linux. Microsoft's Salesforce complaint doesn't involve any allegations over open-source software.

Post updated at 4 p.m. with additional background